The US population is aging and individuals are keeping more of their teeth into old age compared to previous generations. These trends suggest the prevalence of root caries and expenditures to treat them will continue to rise. More research is needed to better understand how diet affects root caries risk. Most of our knowledge about dietary risk factors for caries, particularly sugars, comes from studies of coronal (enamel) caries, primarily in children, and conducted prior to the widespread availability of fluoride. It is not clear how relevant these studies are to the current problem of root caries in older adults. Root caries can develop in a less acidic environment than coronal caries. Older adults tend to consume less sugar than younger age groups. Therefore, the roles of other dietary factors, both cariogenic and protective, need to be examined. The study of diet and root caries is complex because intakes of various nutrients are highly correlated. Analysis of dietary patterns is a methodological approach that has been used in the study of diet and other chronic diseases. The aim of this research is to investigate dietary patterns that are associated with root caries risk using existing data from two study populations. The first population is the prospective VA Dental Longitudinal Study (DLS) of adult men which has collected 2 decades of data on root caries and restorations, diet, and other oral health, lifestyle, and medical variables. The men are not VA patients, but are volunteers in a VA study who receive medical and dental care from the private sector. Root caries prevalence and incidence will be estimated from 563 DLS subjects who have participated in two or more dental examinations in the past 20 years. Our primary hypothesis is that root caries prevalence, incidence and severity are reduced among older men who follow a dietary pattern that is high in fruits, vegetables, low-fat dairy and whole grains, even in the presence of moderate sugar intake. To address this hypothesis, we will use cluster analysis to identify dietary patterns from food frequency questionnaires in the DLS that are associated with reduced risk of root caries. We will use multivariable logistic, survival and Poisson regression analyses to estimate the primary and secondary root caries prevalence, incidence and severity associated with the dietary patterns. All models will control for important confounders. The dietary patterns will be validated in the second population, the cross-sectional NHANES survey conducted in 2003-04. In this survey, 5122 adults received dental examinations and completed food frequency questionnaires. Although NHANES only provides measures of root caries prevalence, sample weights can be used to derive nationally representative estimates of disease in the population as a whole and in gender- and ethnic-specific subgroups. An important result of this research is the potential for creating a consistent set of dietary recommendations for patients and the public that integrates oral health into overall health promotion strategies. PUBLIC HEALTH RELEVANCE: Root decay is expected to be a growing problem among older adults in the US as people live longer and keep more of their teeth. This study will identify dietary patterns that are associated with root decay in a group of older men and in a nationally representative sample of adult men and women. The findings may help to define healthy eating patterns that reduce the risk of root decay.